Electrochemical Measurements Of The Concentrations Of Chromium, Iron And Copper Ions In The Chromium Plating Solution

Chromium plating has a very important position in the electroplating industry. The concentration of chromic anhydride, iron and copper directly affects the quality of the coating. It is very important in development of the chrome plating process in order to analyse the concentration of chromic anhydride, iron and copper with a quick, accuract, easy and lowcost method. The existing analysis methods have the disadvantages of bad selectivity, low sensitivity and high cost. To solve these problems, this paper uses electrochemical methods. The concentration of chromic anhydride, iron and copper was studied by electrochemical methods. The analysis and research were based on the concentration of chromic anhydride in common chrome plating solution by linear sweep voltammetry, and studied the high and low concentrations of ion and copper. In addition, the permselectivity of cation-exchange membrane to Cu2+and Fe3+was studied. It provides technology supports for simultaneous analysing of chromic anhydride, iron and copper. The main results are summarized as follows;The linear sweep voltammetry method was chosen to study the chrome plating solution. We can find that the reducing peak potential is about0.5V. And the redox system is irreversible. The reductive peak currents were linear with concentrations of chromic anhydride in the range of2.5to20g·L-1. Analyzing a factory chrome plating solution, the error is within5%. The results meet the technical requirements. So we can quickly and exactly analyze the concentration of chromic anhydride from the chrome plating solution within high chromic anhydride and low ion and copper. This study provides an effective method for on-line monitoring.Linear sweep voltammetry and cyclic voltammetry were chosen to study the CuSO4and Fe2(SO4)3solution. We can find that the reducing peak potentials of Cu2+and Fe3+are about-0.1V and0.33V. The redox systems both Cu2+and Fe3+are irreversible. The reductive peak currents of Cu2+were linear with concentrations of CuSO4in the range of0.156to0.625g·L-1. In addition, the reductive peak currents of Fe3+were linear with concentrations of Fe(SO4)3in the range of0.625to5.00g·L-1. Potentiometric analysis is chosen to study the CuSO4solution. Open circuit voltage E and lg[Cu2+] had a good linear relationship. Square wave voltammetry is chosen to study the CuSO4and Fe2(SO4)3solution. The reductive peak currents of Cu2+were linear with concentrations of Cu2+in the range of2.5to12.5μM. And the reductive peak currents of Fe3+were linear with concentrations of Fe3+in the range of2.0to10.0μM. The research provides some references for the determination of Cu2+and Fe3+in the unknown concentration of CuSO4and Fe2(SO4)3solution.Through SEM of ion exchange cation membrane section after exchange3h, we find Cation exchange membrane has certain permeability to Cu2+. CuSO4solution and H2SO4compensation solution for ion exchange. Square wave voltammetry was chosen to study the H2SO4compensation solution. With the increase of ion exchange time and concentration of CuSO4solution, the reductive peak currents of Cu2+increase. The reductive peak current, concentration of CuSO4and ion exchange time have a corresponding relation. Similarly, Fe2(SO4)3solution and H2SO4compensation solution for ion exchange. With the increase of ion exchange time and concentration of Fe2(SO4)3solution, the reductive peak currents of Fe3+increased. The reductive peak current, concentration of Fe2(SO4)3and ion exchange time have a corresponding relation. The experiment concluded that the cation exchange membrane has a certain permselectivity for Cu2+and Fe3+. Selecting ion exchange time for1h as on-line analysis. This study provides a theoretical basis for analyzing Fe3+and Cu2+in the chrome plating solution by online monitoring.